The present invention relates to light emitting diode systems. It finds particular application in conjunction with the dissipation of heat in light emitting diode systems and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other like applications.
Standard filament bulb flashlight systems dissipate heat by radiating a large percentage of heat to the front lens and a smaller amount to the interior of the flashlight. The heat radiated to the front of the lens is dissipated to the environment. Such conventional heat dissipation systems are suitable for standard filament bulb systems and conventional low power light emitting diode (xe2x80x9cLEDxe2x80x9d) flashlight systems. In other words, current low power LED flashlights have not required a special heat dissipation design.
Relatively high power LED lighting systems have recently become available. These higher power LED lighting systems (e.g., flashlights) dissipate heat by a different heat transfer path than ordinary filament bulb systems. More specifically, these higher power LED lighting systems dissipate a substantial amount of heat via a cathode (negative terminal) leg or through a die attached in a direct die mount device. Therefore, the conventional heat dissipation systems do not adequately reduce heat in higher power LED systems (e.g., flashlights). Consequently, the higher power LED systems tend to run at higher operating temperatures.
Higher operating temperatures degrade the performance of the high power LED lighting systems. Experiments with a wide variety of LEDs have suggested an exponential relationship of the life expectancy of an LED versus operating temperature. The well known Arhenius function is an approximate model for LED degradation: D varies according to tekT, where D is the degradation, t is time, e the base of natural logarithms, k an activation constant, and T the absolute temperature in degrees Kelvin. While this formulation is necessarily inexact, and is clearly device dependent, within a given LED family, the empirical data can be modeled satisfactorily. The impact of this realization is dramatic. While room temperature (25xc2x0 C.) lifetimes may in fact approach one hundred thousand hours, operation at close to 90xc2x0 C. may reduce an LED life to less than seven thousand hours.
Because no effective means has been available for passively cooling an LED die in higher power LED lighting systems, the operating life of LEDs used in higher power lighting applications has been shortened.
The present invention provides a new and improved apparatus and method which overcomes the above-referenced problems and others.
A heat dissipating system for an LED lighting device includes an LED, a die for supplying electrical power to the LED, a thermally conductive material secured to the die, and an outer body around the thermally conductive material. Heat within the die is conducted to the thermally conductive material. The heat is transferred from the thermally conductive material to an external environment via the outer body.
In accordance with one aspect of the invention, a die support is between the die and the thermally conductive material. The heat within the die is transferred to the thermally conductive material via the die support.
In accordance with another aspect of the invention, the thermally conductive material includes a metal material.
In accordance with a more limited aspect of the invention, the thermally conductive material is a one-piece casing of the metal material.
In accordance with another aspect of the invention, the thermally conductive material is a sleeve assembly.
In accordance with another aspect of the invention, a circuit board is secured to the conductive material.
In accordance with another aspect of the invention, the heat is transferred from the thermally conductive material to the outer body via conduction.
In accordance with a more limited aspect of the invention, the heat is transferred from outer body to the external environment via convection.
In accordance with another aspect of the invention, the heat is transferred from the thermally conductive material to the outer body via a contact between the conductive material and the outer body.
In accordance with another aspect of the invention, a thermally conductive adhesive between the conductive material and the outer body transfers the heat from the thermally conductive material to the outer body.
One advantage of the present invention is that it provides a highly efficient heat dissipating design for higher power LED lighting systems.
Another advantage of the present invention is that it provides a longer lifetime for LED lighting systems.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.